8.1 Welding Safety Hazards and Prevention
Key Takeaways
ANSI Z49.1, 'Safety in Welding, Cutting, and Allied Processes,' plus OSHA 29 CFR 1910/1926 govern welding safety on Part A
Apply the hierarchy of controls (elimination, substitution, engineering, administrative, PPE) — PPE is the last resort
Primary voltage (~230–575 V) is the lethal input; secondary/open-circuit voltage (20–100 V) is lower but still dangerous in wet/confined work
Arc radiation causes arc eye (UV) and retinal damage (IR); filter shade number increases with arc current and varies by process
Stainless steel → hexavalent chromium (lung cancer); galvanized → zinc/metal fume fever; control with local exhaust ventilation
Fire: clear combustibles 35 ft, hot-work permit, fire watch (OSHA 30 min / NFPA 51B 60 min); cylinders upright, O₂ ≥20 ft from fuel gas, flashback arrestors
Confined space (OSHA 1910.146): test O₂ first (safe 19.5%–23.5%), then combustibles, then toxics; permit, ventilation, outside attendant, rescue plan
Welding Safety and the CWI
ANSI Z49.1, Safety in Welding, Cutting, and Allied Processes, published by the American Welding Society (AWS), is a principal welding-safety reference. Applicable OSHA requirements also appear in 29 CFR 1910 (general industry) and 1926 (construction). A Certified Welding Inspector (CWI) is not a substitute for a safety officer, but the inspector is often the most knowledgeable person on the floor and is expected to recognize unsafe conditions and stop work that endangers personnel. Z49.1 addresses hazards into the same categories the exam tests: electric shock, arc radiation, fumes and gases, fire and explosion, compressed-gas hazards, and confined-space hazards.
The Hierarchy of Controls
ANSI Z49.1 and OSHA apply the standard hierarchy of controls to every hazard — pick the highest control that is feasible before relying on the lowest:
| Rank | Control | Welding example |
|---|---|---|
| 1 | Elimination/substitution | Use a low-fume electrode; weld off-site away from the public |
| 2 | Engineering controls | Local exhaust ventilation (LEV); welding screens; insulated holders |
| 3 | Administrative controls | Hot-work permits; rotating workers to limit exposure; training |
| 4 | PPE (last resort) | Helmet with proper shade, FR clothing, respirator, gloves |
Personal protective equipment (PPE) is the LAST line of defense, not the first — a common exam trap is to choose "give the welder a respirator" when ventilation (an engineering control) is the better answer.
The Major Hazard Categories
Memorize the categories the way ANSI Z49.1 frames them. Electric shock is the most serious immediate hazard because it can kill instantly. Burns are the most common injury, caused by arc rays, spatter, hot metal, and slag. Arc radiation produces ultraviolet (UV) and infrared (IR) energy that injures the eyes and skin. Fumes and gases create the most significant long-term (chronic) health risk. Fire and explosion are the leading cause of property loss, and confined-space work multiplies every other hazard. The remainder of this section drills into each category with the exact numbers the exam expects.
Electric Shock — Primary vs. Secondary Voltage
Arc-welding power sources draw high-voltage utility power and step it down to a usable welding circuit, so a CWI must distinguish the two voltages.
| Voltage | Where it appears | Typical value | Risk |
|---|---|---|---|
| Primary (input) voltage | The line feeding the power source (utility/branch circuit) | 230–575 V AC | Can be instantly fatal; only qualified electricians work inside the case |
| Secondary (open-circuit) voltage, OCV | The welding circuit between electrode and work before the arc strikes | Typically 20–100 V, commonly up to ~80 V OCV | Lower, but still dangerous — most welder shocks come from here |
A dangerous misconception is that the secondary circuit is "safe." Secondary voltage can be lethal under the right conditions — wet skin, perspiration, damp clothing, or a confined metal space all drop body resistance and let current flow. Prevention measures (ANSI Z49.1 / OSHA 1910.252):
- Never touch the electrode, wire, or live metal parts with bare skin or wet gloves
- Keep the work and yourself dry; never stand or kneel in water while welding
- Ground the workpiece and the equipment frame properly; inspect cables for bare spots or cracked insulation
- Use fully insulated electrode holders and ensure the work clamp makes solid contact
- In damp or confined locations, use equipment with reduced OCV or a voltage-reducing device (VRD)
- Turn the machine off before changing electrodes or leaving the station; never coil the electrode cable around the body
Arc Radiation and Eye Protection
The welding arc emits ultraviolet (UV), visible, and infrared (IR) radiation. UV causes arc eye (also called welder's flash or photokeratitis) — a painful, gritty, delayed inflammation of the cornea — plus skin burns like a severe sunburn. IR can cause retinal burns and cataracts over time. The defense is a welding helmet with a filter plate of the correct shade number, plus safety glasses with side shields worn underneath, and full skin coverage.
Selecting the Filter Lens Shade Number
The shade number scales with the brightness of the arc, which rises with arc current (amperage) and varies by process. Higher current = higher (darker) shade. The table below gives OSHA minimum protective shades and the darker ANSI/AWS suggested shades (Z49.1 Table 1). Always start with the suggested shade and lighten only enough to see the weld pool clearly.
| Process | Arc current (A) | OSHA min. shade | ANSI/AWS suggested |
|---|---|---|---|
| SMAW | < 60 | 7 | — |
| SMAW | 60–160 | 8 | 10 |
| SMAW | 160–250 | 10 | 12 |
| SMAW | 250–550 | 11 | 14 |
| GMAW/FCAW | < 60 | 7 | — |
| GMAW/FCAW | 60–160 | 10 | 11 |
| GMAW/FCAW | 160–250 | 10 | 12 |
| GMAW/FCAW | 250–500 | 10 | 14 |
| GTAW | < 50 | 8 | 10 |
| GTAW | 50–150 | 8 | 12 |
| GTAW | 150–500 | 10 | 14 |
| Plasma arc cutting (PAC) | < 300 | 8 | 9 |
| Plasma arc cutting (PAC) | 300–400 | 9 | 12 |
| Air carbon arc (CAC-A), light | < 500 | 10 | 12 |
| Air carbon arc (CAC-A), heavy | 500–1000 | 11 | 14 |
| Oxyfuel gas welding/cutting | (torch, by thickness) | 3–6 | 4–8 |
Exam trap: GTAW (TIG) produces more UV per ampere than SMAW, so it often needs a darker shade than its low current would suggest. And oxyfuel work needs only a shade 3–6 (a flame, not an arc), but it still needs eye protection.
Fumes and Gases
Welding fumes are fine metallic-oxide particulate formed when vaporized metal condenses; gases (carbon monoxide, ozone, nitrogen oxides, shielding-gas displacement) form separately. ANSI Z49.1 requires that breathing-zone concentrations stay below the applicable OSHA Permissible Exposure Limit (PEL) or ACGIH Threshold Limit Value (TLV). The first control is ventilation, not respirators: provide local exhaust ventilation (LEV) at the arc, or adequate general/mechanical ventilation, and use respiratory protection only when ventilation cannot reach the limits.
| Fume/gas | Source | Health effect |
|---|---|---|
| Hexavalent chromium (Cr⁶⁺) | Stainless steel, chromium alloys | Lung cancer; very low PEL (5 µg/m³) |
| Manganese | Most steel electrodes/wires | Neurological damage (manganism) |
| Zinc oxide | Galvanized (zinc-coated) steel | Metal fume fever (flu-like) |
| Cadmium | Plated/coated metals, some brazing alloys | Acute lung injury, can be fatal |
| Lead | Painted/coated steel | Lead poisoning (CNS, kidney) |
| Ozone (O₃) | UV acting on air, esp. GMAW/GTAW on aluminum | Respiratory irritation, pulmonary edema |
| Carbon monoxide (CO) | CO₂ shielding gas breakdown | Asphyxiant; binds hemoglobin |
Welders should keep their head out of the fume plume, position work so natural draft carries fumes away, and never weld on galvanized, cadmium-plated, or painted metal without dedicated ventilation. The exam loves the stainless-steel → hexavalent chromium and galvanized → zinc/metal-fume-fever pairings.
Fire and Explosion Prevention
Sparks and molten spatter can travel and ignite combustibles up to 35 ft (10 m) away — air carbon arc cutting throws sparks even farther. OSHA 1910.252 and NFPA 51B set the rules:
- Clear combustibles within 35 ft; if they cannot be moved, cover with fire-resistant blankets/guards
- Keep a charged Class ABC fire extinguisher within reach
- Issue a hot-work permit for any cutting/welding outside a designated, fire-safe welding area
- Post a fire watch during the work and afterward — OSHA requires a minimum of 30 minutes after work stops; NFPA 51B (2019 and later) extends this to 60 minutes, with the area monitored for up to 3 additional hours where required
- Never weld or cut on containers that held flammables until they are purged, cleaned, or inerted — explosion risk
Compressed-Gas Cylinder Safety
Oxyfuel and shielding-gas cylinders are high-pressure vessels (oxygen ~2,200 psi). ANSI Z49.1 and OSHA 1910.253 require:
- Store and use cylinders upright and secured (chain/strap) to a fixed support; never let them tip or roll
- Keep the valve protection cap on whenever the regulator is removed or the cylinder is moved/stored
- Separate oxygen from fuel-gas cylinders and combustibles by at least 20 ft, or by a noncombustible barrier ≥5 ft high with a ≥½-hour fire rating when in storage
- Never use oxygen as a substitute for compressed air (clothing/oil + oxygen = fire)
- Keep cylinders, regulators, and fittings free of oil and grease, especially on oxygen service
- Fit flashback arrestors and reverse-flow (backflow) check valves on both the oxygen and fuel-gas lines to stop a flame or gas from traveling back into the hose/cylinder
- "Crack" a cylinder valve before attaching a regulator to blow out dirt, and open fuel-gas valves no more than ¾–1 turn so they can be shut quickly
PPE and Confined-Space Entry
PPE for welding includes the helmet with correct filter shade, safety glasses with side shields beneath it, flame-resistant (FR) clothing buttoned to the neck with no cuffs or open pockets, leather gloves and aprons/leathers as needed, and respiratory protection when ventilation is insufficient. 146: test the atmosphere in order oxygen first, then combustibles, then toxics. 5% is oxygen-enriched (a fire accelerant). Provide forced ventilation, an entry permit, a trained attendant stationed outside, and a rescue plan.
Cylinders are never taken into a confined space, and shielding gases must not be left running inside (they displace oxygen).
| Hazard | Key threshold/rule | Primary control |
|---|---|---|
| Electric shock | Primary 230–575 V; OCV up to ~80 V | Insulate, ground, keep dry, VRD |
| Arc radiation | Shade scales with amperage | Correct-shade helmet, FR coverage |
| Fumes/gases | Stay below PEL/TLV (Cr⁶⁺ 5 µg/m³) | Local exhaust ventilation |
| Fire/explosion | 35 ft clearance; 30/60-min fire watch | Hot-work permit, extinguisher |
| Compressed gas | O₂/fuel ≥20 ft apart in storage | Secure upright, caps, flashback arrestors |
| Confined space | O₂ 19.5%–23.5% | Test, ventilate, permit, attendant |
Which statement about welding electrical shock is correct?
Secondary (open-circuit) welding voltage cannot harm a worker
Primary voltage of 230–575 V is the input to the power source and can be fatal
Grounding the workpiece increases the risk of shock
Open-circuit voltage is typically 600 V or higher
According to ANSI/AWS-suggested values, an SMAW operation at 200 A should use approximately what filter shade?
Shade 6
Shade 8
Shade 12
Shade 4
In the hierarchy of controls, which option is the LEAST preferred and used only as a last resort?
Personal protective equipment (respirator, helmet)
Engineering controls (local exhaust ventilation)
Substitution (low-fume electrodes)
Elimination of the hazard
When testing the atmosphere of a confined space before welding, in what order must the tests be performed?
Toxics first, then oxygen, then combustibles
Combustibles first, then toxics, then oxygen
Order does not matter as long as all three are tested
Oxygen first, then combustibles, then toxics
How must oxygen cylinders be separated from fuel-gas cylinders in storage?
At least 20 ft apart, or by a noncombustible barrier ≥5 ft high with a ≥½-hour fire rating
At least 5 ft apart with no barrier needed
Stored together as long as both are upright
At least 100 ft apart in all cases
Welding on stainless steel is most associated with which serious chronic health hazard?
Metal fume fever from zinc oxide
Lead poisoning
Hexavalent chromium exposure (lung cancer)
Carbon monoxide asphyxiation
Sections you finish are checked off in the contents.